Drive system incorporating a hybrid fuel cell

ABSTRACT

A vehicle drive system powered by a hybrid fuel cell including at least one cathode, at least one anode, and at least one auxiliary electrode. The auxiliary electrode works in combination with the anode to provide a current as a rechargeable battery while the anode and cathode work in combination to provide an electrical current as a fuel cell. The cathode and the auxiliary electrode may operate alone or in tandem to provide an electrical current.

CROSS REFERENCE TO RELATED APPLICATIONS

The present invention is a continuation-in-part of, and is entitled tothe benefit of the earlier filing date and priority of, co-pending U.S.patent application Ser. No. 10/636,152, which is assigned to the sameassignee as the current application, entitled “A HYBRID FUEL CELL”,filed Aug. 7, 2003, the disclosure of which is hereby incorporated byreference.

FIELD OF THE INVENTION

The present invention generally relates to fuel cells. Moreparticularly, the present invention relates to fuel cells having abuilt-in battery used to supplement the power output of the fuel celland provide instant start-up.

BACKGROUND

As the world's population expands and its economy increases, theincrease in the atmospheric concentrations of carbon dioxide is warmingthe earth causing climate changes. However, the global energy system ismoving steadily away from the carbon-rich fuels whose combustionproduces the harmful gas. Experts say atmospheric levels of carbondioxide may be double that of the pre-industrial era by the end of thenext century, but they also say the levels would be much higher exceptfor a trend toward lower-carbon fuels that has been going on for morethan 100 years. Furthermore, fossil fuels cause pollution and are acausative factor in the strategic military struggles between nations.Furthermore, fluctuating energy costs are a source of economicinstability worldwide.

In the United States, it is estimated, that the trend towardlower-carbon fuels combined with greater energy efficiency has, since1950, reduced by about half the amount of carbon spewed out for eachunit of economic production. Thus, the decarbonization of the energysystem is the single most important fact to emerge from the last 20years of analysis of the system. It had been predicted that thisevolution will produce a carbon-free energy system by the end of the21^(st) century. The present invention is another product which isessential to shortening that period to a matter of years. In the nearterm, hydrogen will be used in fuel cells for cars, trucks andindustrial plants, just as it already provides power for orbitingspacecraft. But, with the problems of storage and infrastructure solved(see U.S. application Ser. No. 09/444,810, entitled “A Hydrogen-basedEcosystem” filed on Nov. 22, 1999 for Ovshinsky, et al., which is hereinincorporated by reference and U.S. patent application Ser. No.09/435,497, entitled “High Storage Capacity Alloys Enabling aHydrogen-based Ecosystem”, filed on Nov. 6, 1999 for Ovshinsky et al.,which is herein incorporated by reference), hydrogen will also provide ageneral carbon-free fuel to cover all fuel needs.

Hydrogen is the “ultimate fuel.” In fact, it is considered to be “THE”fuel for the future. Hydrogen is the most plentiful element in theuniverse (over 95%). Hydrogen can provide an inexhaustible, clean sourceof energy for our planet which can be produced by various processes.Utilizing the inventions of subject assignee, the hydrogen can be storedand transported in solid state form in trucks, trains, boats, barges,etc. (see the '810 and '497 applications).

A fuel cell is an energy-conversion device that directly converts theenergy of a supplied gas into an electric energy. While other fuels arebeing tried, hydrogen is the primary fuel of choice because of itssimplicity and the nature of the end product. Researchers have beenactively studying fuel cells to utilize the fuel cell's potential highenergy-generation efficiency. The base unit of the fuel cell is a cellhaving an oxygen electrode, a hydrogen electrode, and an appropriateelectrolyte. Fuel cells have many potential applications such assupplying power for transportation vehicles, replacing steam turbinesand power supply applications of all sorts. Despite their seemingsimplicity, many problems have prevented the widespread usage of fuelcells.

Fuel cells, like batteries, operate by utilizing electrochemicalreactions. Unlike a battery, in which chemical energy is stored withinthe cell, fuel cells generally are supplied with fuel (reactants) fromoutside the cell. Barring failure of the electrodes, as long as thefuel, preferably hydrogen, and oxidant, typically air or oxygen, aresupplied and the reaction products are continuously removed from thesystem, the cell continues to operate.

Fuel cells offer a number of important advantages over internalcombustion engine or other energy generating systems. These includerelatively high efficiency, environmentally clean operation especiallywhen utilizing hydrogen as a fuel, high reliability, few moving parts,and quiet operation. Fuel cells potentially are more efficient thanother conventional power sources based upon the Carnot cycle.

The major components of a typical fuel cell are the hydrogen electrodefor hydrogen oxidation reaction and the oxygen electrode for oxygenreduction reaction, both being positioned in a cell containing anelectrolyte (such as an alkaline electrolytic solution). Typically, thereactants, such as hydrogen and oxygen, are respectively fed through aspecially designed porous hydrogen electrode and oxygen electrode andbrought into surface contact with the electrolyte. The particularmaterials utilized for the hydrogen electrode and oxygen electrode areimportant since they must act as efficient catalysts for the reactionstaking place.

In a hydrogen-oxygen alkaline fuel cell, the reaction at the hydrogenelectrode occurs between hydrogen fuel and hydroxyl ions (OH⁻) presentin the electrolyte, which react to form water and release electrons asshown in the overall reaction:H₂+2OH⁻->2H₂O+2e⁻At the oxygen electrode, oxygen, water, and electrons react in thepresence of the oxygen electrode catalyst to reduce the oxygen and formhydroxyl ions (OH⁻):O₂+2H₂O+4e⁻->4OH⁻The flow of electrons is utilized to provide electrical energy for aload externally connected to the hydrogen and oxygen electrodes.

The catalyst in the hydrogen electrode of the alkaline fuel cell has tonot only split molecular hydrogen to atomic hydrogen, but also oxidizethe atomic hydrogen to release electrons. The overall reaction can beseen as (where M is the catalyst):M+H₂->2 MH->M+2H⁺+2e⁻Thus the hydrogen electrode catalyst must efficiently dissociatemolecular hydrogen into atomic hydrogen. Using conventional hydrogenelectrode materials/catalysts, the dissociated hydrogen atoms remaintransitional and the hydrogen atoms can easily recombine to formmolecular hydrogen if they are not used directly in the oxidationreaction as a number of conditions can prevent a quick oxidativeresponse.

In a zinc-air fuel cell, a type of metal-air fuel cell, the reaction atthe anode occurs between the zinc contained in the anode and hydroxylions (OH⁻) present in the electrolyte, which react to release electrons:Zn->Zn⁺²+2e⁻Zn⁺²+2(OH⁻)->Zn(OH)₂Zn(OH)₂+2(OH)—->ZnO₂ ⁻²+2H₂OAt the cathode, oxygen, water, and electrons react in the presence ofthe oxygen electrode catalyst to reduce the oxygen and form hydroxylions (OH⁻):O₂+2H₂O+4e⁻->4OH⁻.The flow of electrons is utilized to provide electrical energy for aload externally connected to the hydrogen and oxygen electrodes.

Fuel cells, when used to power vehicles, are often used with anauxiliary battery pack because of the general inability of fuel cells toprovide power instantly upon start-up or provide increased bursts ofpower for sudden acceleration. Such vehicles are generally termed hybridelectric vehicles (HEV). The auxiliary battery supplements the fuel cellpower output during conditions requiring high power output, such asduring start-up or sudden acceleration. The auxiliary battery may beused for the absorption of regenerative braking power.

Hybrid systems have been divided into two broad categories, namelyseries and parallel systems, which may include an internal combustionengine or fuel cell supplied. The internal combustion engine is suppliedwith a combustible fuel while the fuel cell is supplied with hydrogen ora fuel capable of providing hydrogen atoms needed for power generation.In a typical series hybrid vehicle system utilizing an internalcombustion engine, as shown in FIG. 1, a battery 1 powers an electricpropulsion motor 2 which is used to propel a vehicle 3 and an internalcombustion engine 4 a is used to recharge the battery 1. In a typicalseries hybrid vehicle system utilizing a fuel cell, as shown in FIG. 2,a battery 1 powers an electric propulsion motor 2 which is used topropel a vehicle 3 and the fuel cell 4 b is used to recharge thebattery. In a typical parallel hybrid vehicle system utilizing aninternal combustion engine, as shown in FIG. 3, both the internalcombustion engine 4 a and the battery 1 in conjunction with an electricmotor 2 can be used, either separately or together, to propel a vehicle3. The internal combustion engine 4 a may also be used to recharge thebattery 1. In a typical parallel hybrid vehicle system utilizing a fuelcell, as shown in FIG. 4, both the battery 1 and the fuel cell 4 b areused to power an electric motor 2 which propels the vehicle 3. The fuelcell 4 b may also be used to recharge the battery 1. In the types ofvehicles utilizing a parallel hybrid vehicle system, the battery isusually used only in short bursts to provide increased power upon demandafter which the battery is recharged using the internal combustionengine or via feedback from a regenerative braking process. Shown inFIG. 5 and FIG. 6, are further detailed schematics of hybrid systemsutilizing fuel cells. The schematic shown in FIG. 5, shows an example ofa parallel hybrid vehicle system including a battery and a fuel cell 4b, both of which supply power to a power logic control 6, which powersan electric motor 2, and a hydrogen storage unit 5, which provideshydrogen to the fuel cell. Power is also supplied from the power logiccontrol 6 to a hotel load 7, which provides power to other vehiclecomponents. In this design, both the fuel cell 4 b and the battery 1power the electric motor 2, while power from the fuel cell 4 b may beused to recharge the battery 1. Power may also be generated throughregenerative braking and used to recharge the battery 1. In this system,the battery is used for on demand surge power and the fuel cell is usedfor on demand load leveling power. Since the battery is used only for ondemand surge power, the battery requires only a small amount of energystorage. The schematic in FIG. 6 shows range extender series hybridsystem design including a battery 1 and a fuel cell 4 b, both of whichsupply power to a power logic control 6, which provides power to anelectric motor 2, and a hydrogen storage unit 5, which provides hydrogento the fuel cell. Power is also supplied from the power logic control 6to a hotel load 7, which provides power to other vehicle components. Inthis system, the battery 1 is essentially powering the electric motor 2while the power from the fuel cell 4 b is used to recharge the battery1. This system requires a large amount of battery energy storage withthe range of the vehicle being related to the amount of hydrogen storedonboard the vehicle.

There are further variations within these two broad categories. Onevariation is made between systems which are “charge depleting” in theone case and “charge sustaining” in another case. In the chargedepleting system, the battery charge is gradually depleted during use ofthe system and the battery thus has to be recharged periodically from anexternal power source, such as by means of connection to public utilitypower. In the charge sustaining system, the battery is recharged duringuse in the vehicle, through regenerative braking and also by means ofelectric power supplied from the a generator powered by the internalcombustion engine so that the charge of the battery is maintained duringoperation.

There are many different types of systems that fall within thecategories of “charge depleting” and “charge sustaining” and there arethus a number of variations within the foregoing examples which havebeen simplified for purposes of a general explanation of the differenttypes. However, it is to be noted in general that systems which are ofthe “charge depleting” type typically require a battery which has ahigher charge capacity (and thus a higher specific energy) than thosewhich are of the “charge sustaining” type if a commercially acceptabledriving range (miles between recharge) is to be attained in operation.

A key enabling technology for HEVs is having an energy storage systemhaving a high energy density while at the same time being capable ofproviding very high power. Such a system allows for recapture of energyfrom braking currents at very high efficiency while enabling the designof a smaller battery pack.

A typical auxiliary battery pack as used in HEV applications is a nickelmetal hydride battery pack. In general, nickel-metal hydride (Ni-MH)cells utilize a negative electrode comprising a metal hydride activematerial that is capable of the reversible electrochemical storage ofhydrogen. Examples of metal hydride materials are provided in U.S. Pat.Nos. 4,551,400, 4,728,586, and 5,536,591 the disclosures of which areincorporated by reference herein. The positive electrode of thenickel-metal hydride cell comprises a nickel hydroxide active material.The negative and positive electrodes are spaced apart in the alkalineelectrolyte.

Upon application of an electrical current across a Ni-MH cell, the Ni-MHmaterial of the negative electrode is charged by the absorption ofhydrogen formed by electrochemical water discharge reaction and theelectrochemical generation of hydroxyl ions:

The negative electrode reactions are reversible. Upon discharge, thestored hydrogen is released to form a water molecule and release anelectron.

The charging process for a nickel hydroxide positive electrode in analkaline electrochemical cell is governed by the following reaction:

During charge, the nickel hydroxide is oxidized to form nickeloxyhydroxide and during discharge, the nickel oxyhydroxide is reduced toform nickel hydroxide as shown by the following reaction:

While the inclusion of an auxiliary battery pack working in conjunctionwith a fuel cell has many advantages for powering vehicles, such systemsstill have disadvantages upon implementation in a vehicle. Thedisadvantages of including a battery along with the fuel cell mayinclude increased weight, increased space, extra terminals, inter cellconnects, increased cost, increased maintenance, etc. Improvements inthese areas will help fuel cells to become the standard source of powerfor vehicles and many other applications.

SUMMARY OF THE INVENTION

The present invention discloses a vehicle drive system comprising anelectric motor, a hybrid fuel cell comprising a fuel cell portion and arechargeable battery portion, and a hydrogen storage unit for storingand supplying hydrogen to said hybrid fuel cell. The fuel cell portionand the rechargeable battery portion being adapted to operate alone orin tandem to power the electric motor and being adapted to share atleast one reactant.

The hybrid fuel cell of the vehicle drive system further comprises ananode section including one or more anodes shared between the fuel cellportion and the rechargeable battery portion. The one more anodes maycomprise an 90 to 99 weight percent of an anode active materialincluding zinc, cadmium, magnesium, or aluminum, and 1 to 10 weightpercent of a binder material.

The one or more anodes may also comprise a 0.0 to 99.0 weight percent ofa hydrogen storage material, 0.0 to 88.0 weight percent Raney nickel,4.0 to 12.0 weight percent of a binder material, and 0.0 to 5.0 weightpercent of a conductive material. The conductive material may comprisegraphite or graphitized carbon. The hydrogen storage material maycomprise Rare-earth metal alloys, Misch metal alloys, zirconium alloys,titanium alloys, magnesium/nickel alloys, or mixtures thereof.

The fuel cell portion comprises at least one cathode in electricalcommunication with the anode. The cathode may comprise a carbon matrixwith an active catalyst material catalytic toward the dissociation ofmolecular oxygen dispersed therein. The active catalyst material may beselected from silver, silver alloys, silver oxide, cobalt, cobalt oxide,cobalt manganese oxide, nickel, manganese oxide, manganese dioxide,pyrolyzed macrocyclics, or combinations thereof. The cathode may furthercomprise a peroxide decomposing material.

The rechargeable battery portion comprises at least one auxiliaryelectrode in electrical communication with said anode. The auxiliaryelectrode comprises a positive electrode material. The vehicle drivesystem according to claim 15, wherein said auxiliary electrode may be anickel electrode or a silver electrode. The positive electrode materialmay comprise 75 to 85 weight percent of a positive electrode activematerial, 0.0 to 10 weight percent cobalt, 0.0 to 10 weight percentcobalt oxide, and 0.0 to 4.0 weight percent of a binder material. Thepositive electrode active material may be selected from nickelhydroxide/nickel oxyhydroxide, copper oxide, silver oxide, manganesedioxide, or combinations thereof.

The rechargeable battery portion may be adapted to accept an electricalcurrent from a source of power external to the hybrid fuel cell. Therechargeable battery portion may be adapted to accept an electricalcurrent produced by the fuel cell portion. The fuel cell portion andsaid rechargeable battery portion share an electrolyte.

The hydrogen storage unit may comprise a pressure containment vessel atleast partially filled with a hydrogen storage alloy or a pressurecontainment vessel adapted to store hydrogen in liquid or gaseous form.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1, is a schematic representation of a series hybrid electricvehicle drive system including an internal combustion engine and arechargeable battery.

FIG. 2, is a schematic representation of a series hybrid electricvehicle drive system including a fuel cell and a rechargeable battery.

FIG. 3, is a schematic representation of a parallel hybrid electricvehicle system including an internal combustion engine and arechargeable battery.

FIG. 4, is a schematic representation of a parallel hybrid electricvehicle system including a fuel cell and a rechargeable battery.

FIG. 5, is a detailed schematic representation of a parallel fuel cellhybrid drive system.

FIG. 6, is a detailed schematic representation of a series fuel cellhybrid drive system.

FIG. 7, is a schematic of a drive system in accordance with the presentinvention.

FIG. 8, shows an embodiment of a hydrogen-oxygen alkalineelectrochemical cell unit in accordance with the present invention.

FIG. 9, shows an exploded view of the electrochemical cell unit depictedin FIG. 1.

FIG. 10, shows an embodiment of a metal-air alkaline electrochemicalcell unit in accordance with the present invention.

FIG. 11, shows an exploded view of the electrochemical cell unitdepicted in FIG. 3.

FIG. 12, shows the performance during fuel cell mode and hybrid mode ofan embodiment of a hydrogen-oxygen hybrid fuel cell in accordance withthe present invention.

FIG. 13, shows the voltage of an embodiment of a hydrogen-oxygen hybridfuel cell in accordance with the present invention upon accepting acharging current.

FIG. 14, shows the performance during fuel cell mode and hybrid mode ofan embodiment of a metal-air hybrid fuel cell in accordance with thepresent invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS OF THE INVENTION

The present invention discloses a vehicle drive system including ahybrid fuel cell with an insitu rechargeable battery which can operatein 1) a fuel cell mode, 2) a rechargeable battery mode, and 3) a hybridmode which operates as a combined fuel cell/rechargeable battery. Aschematic representation of a drive system in accordance with thepresent invention is shown in FIG. 7. The hybrid fuel cell 4 c powers anelectric motor 2 which propels the vehicle 3. During operation, hydrogenis supplied to the hybrid fuel cell 4 c from a hydrogen storage unit 5.The drive system does not require the use of a second power source asrequired by hybrid vehicles. The hybrid fuel cell is able to generatesufficient power during start-up, sudden acceleration, and under manyother conditions thereby eliminating the need for a secondary source ofpower to supplement the fuel cell as needed.

The hydrogen storage unit may store hydrogen in liquid, gaseous, ormetal hydride form. Due to the size, mass, and safety concernsassociated with hydrogen storage units storing hydrogen in liquid orgaseous form, the hydrogen storage unit preferably stores hydrogen inmetal hydride form in hydrogen storage alloys. A metal hydride hydrogenstorage unit may be any of the known prior art types of units in whichthe hydrogen storage alloy may be contained. The hydrogen storage unitwill preferably have a means for heating and cooling of the alloy asneeded to charge and discharge hydrogen therefrom. Examples of suchunits are described in U.S. Pat. Nos. 6,293,110, 6,519,951, 6,425,251,6,318,453, 6,378,601, and U.S. patent application Ser. Nos. 10/143,243,09/742,827; and 09/843,201, the disclosures of which are hereinincorporated by reference.

The hybrid fuel cell as used in the drive system of the presentinvention provides for power generation via a fuel cell with thecapability of supplementing the power produced from the fuel cell asneeded with a built-in rechargeable battery. The hybrid fuel cell mayalso work solely as a rechargeable battery as needed. In vehicleapplications, the present invention provides for instant start-upcapability as well as increased power, which is needed for suddenacceleration. The present invention may also be useful as powergenerators for many other applications requiring an instant source ofpower.

The hybrid fuel cell generally comprises one or more electrochemicalcell units connected in series. The number of electrochemical cell unitswithin the hybrid fuel cell may be varied as needed to provide thedesired power output. Fuel cells composed of multiple electrochemicalcell units are described in U.S. patent application Ser. No. 10/650,863,entitled “Air Breathing Fuel Cell Having Bi-cell Unit Cells”, filed onAug. 28, 2003 for Menjak et al., the disclosure of which is hereinincorporated by reference.

Each electrochemical cell unit includes a fuel cell portion and arechargeable battery portion. The fuel cell portion includes at leastone cathode, and the rechargeable battery portion includes at least oneauxiliary electrode. The fuel cell portion and the rechargeable batteryportion may share at least one reactant such as hydrogen and oxygen. Inthe case of a metal-air cell, the fuel cell portion and the rechargeablebattery portion may share a consumable metal electrode comprising zinc,aluminum, cadmium, or magnesium as the anode. The fuel cell portion andthe battery portion share a common anode section including at least oneanode. The cathode in the fuel cell portion and the anode in the anodesection work together as a fuel cell, while the auxiliary electrode inthe rechargeable battery portion and the anode in the anode section worktogether as a rechargeable battery. In addition, the cathode in the fuelcell portion and the auxiliary electrode in the rechargeable batteryportion may work together with the anode section simultaneously in“hybrid mode” thus providing higher power output. The anodes, cathodes,and auxiliary electrodes are in contact with an electrolyte, which maybe in liquid, gel, molten, or solid form. The fuel cell portion and therechargeable battery portion may also share a common electrolyte.

The anodes, cathodes, and auxiliary electrodes may be disposed withinframes in the electrochemical cell units. The frames provide pathwaysfor oxygen, hydrogen, and/or electrolyte to contact the electrodes. Theframes may be constructed from any material resistant to the environmentwithin the electrochemical cell units. Examples of framed electrodes canbe found in U.S. patent application Ser. No. 10/284,817, entitled “FuelCell With Overmolded Electrode Assemblies”, filed on Oct. 31, 2002 forPuttaiah et al., the disclosure of which is herein incorporated byreference.

In many fuel cell systems, the fuel cell works in conjunction with anauxiliary battery pack as a hybrid vehicle system. The battery packprovides energy as needed and is recharged with energy from regenerativebraking and/or external power sources. The hybrid fuel cell inaccordance with the present invention is able to accept energy fromregenerative braking and/or external power sources resulting in chargingof the rechargeable battery portion. During normal operation, the anodesection and cathode in the fuel cell portion work together and functionlike a fuel cell, but upon increased power requirements, such as duringacceleration when used to power a vehicle, the anode section is able towork with the cathode in the fuel cell portion as a fuel cell whileworking with the auxiliary electrode in the rechargeable battery portionas a rechargeable battery thereby providing instant high power outputthrough an increase in current density and/or a decrease inpolarization. The rechargeable battery portion may also work alone withthe anode section to provide power. The capability of the rechargeablebattery portion to work alone is especially useful in vehicleapplications for instant startup.

The fuel cell portion of the electrochemical cell units in accordancewith the present invention may be designed to operate as anhydrogen-oxygen alkaline fuel cell, a metal-air fuel cell, a PEM fuelcell, a direct methanol fuel cell, a molten carbonate fuel cell, a solidoxide fuel cell, or a phosphoric acid fuel cell, provided that all ofthe electrodes including the auxiliary electrode in the rechargeablebattery portion are compatible with the working conditions, and theappropriate electrolyte and temperatures are selected. Preferably, thefuel cell portion of the electrochemical cell units operate as ahydrogen-oxygen alkaline fuel cell or metal-air cell.

A first embodiment of an electrochemical cell unit 10 that may be usedin the drive system in accordance with the present invention is shown inFIG. 8 and FIG. 9. The electrochemical cell unit operates as a hybridhydrogen-oxygen alkaline fuel cell/rechargeable battery. Theelectrochemical cell unit includes a fuel cell portion including onecathode 11 having an oxygen interface and an electrolyte interface, anda rechargeable battery portion including one auxiliary electrode 12 atleast partially immersed in an electrolyte. The fuel cell portion andthe rechargeable battery portion share an anode section including twoanodes 13 each having a hydrogen interface and an electrolyte interface.Oxygen or an oxygen containing stream is supplied to the oxygeninterface of the cathode 11 in the fuel cell portion and hydrogen issupplied to the hydrogen interface of the anodes 13 in the anodesection. Hydrogen enters or is absorbed by the anodes 13 through thehydrogen interface and reacts with the electrolyte at the electrolyteinterface of the anode to form water and release electrons. Oxygenenters the oxygen interface of the cathode 11, is believed to bedissociated into atomic oxygen, and reacts electrochemically utilizingthe incoming electrons to form hydroxyl ions at the electrolyteinterface of the cathode 11. The electrons flowing from the anode to thecathode form the electrical current supplied to the desired externalapplication. When a sudden burst of additional power is needed,electrical current may be supplied from the rechargeable batteryportion. The auxiliary electrode 12 contained in the rechargeablebattery portion works with the anode 13 adjacent to the auxiliaryelectrode 12 in the anode section to provide an electrical current asneeded. The auxiliary electrode is fully charged when it is in itsoxidized state. Upon discharge, the auxiliary electrode undergoesreduction thereby providing an electrical current. The electricalcurrent may be used to supplement the current produced by the fuel cellor may be used alone. To recharge the rechargeable battery portion, acurrent is applied across the anode adjacent to the auxiliary electrodeand auxiliary electrode to re-oxidize the auxiliary electrode.

The anodes 13 and cathodes 11 may be designed such that oxygen orhydrogen enters through the edge of the electrode and flows through theelectrode, or each electrode may have an oxygen or hydrogen contactingside and an electrolyte contacting side. The electrolyte interfaces ofthe cathodes and anodes are in constant contact with an electrolyte,while the auxiliary electrode is at least partially submerged in theelectrolyte. When the anodes and cathodes having an oxygen or hydrogeninterface on one side of the electrode and an electrolyte interface onthe opposing side of the electrode, the electrochemical cell should bedesigned such that the hydrogen or oxygen interfaces of the electrodesremain dry and constantly supplied with hydrogen or oxygen duringoperation.

To optimize the flow of hydrogen, two anodes may be used in the anodesection of electrochemical cell unit as one of the many different designvariations. When using two anodes, the anodes may be placed side by sidewith the hydrogen contacting surfaces of the anodes facing each otherforming a hydrogen chamber between the hydrogen contacting surfaces ofboth the anodes. The anode compositions may differ depending uponwhether they are designed to operate as the anode of the fuel cellportion or the anode of the rechargeable battery portion. A stream ofhydrogen is supplied between the hydrogen electrodes thereby providinghydrogen to the hydrogen contacting sides of the anodes. The cathode 11is placed across from the electrolyte contacting side of one of theanodes, while the auxiliary electrode 12 is placed across from theelectrolyte contacting side of the other anode 13. Distribution plates14 may be placed between the electrodes to aid in the distribution ofelectrolyte, hydrogen, or oxygen to the electrodes. The distributionplates 14 may also provide mechanical support within the electrochemicalcell unit 10. End plates 15 are typically placed at the ends of eachelectrochemical cell unit 10. The endplates 15 may be designed such thatoxygen is allowed to contact the cathode 11 through the end plate 15.The endplates 15 are designed to provide support to each electrochemicalcell unit 10.

A second embodiment of an electrochemical cell unit 10 a that may beused in the drive system in-accordance with the present invention isdepicted in FIG. 10 and FIG. 11. The second embodiment operates as ahybrid metal-air fuel cell/rechargeable battery. The second embodimentincludes at least one cathode 11 having an oxygen interface and anelectrolyte interface, at least one anode 13 a, and at least oneauxiliary electrode 12. The anode 13 a and the auxiliary electrode 12are at least partially submerged in an alkaline electrolyte solution.Unlike the hybrid hydrogen-oxygen alkaline fuel cell, the anode 13 a forthe metal-air cell does not need to be supplied with hydrogen. The anode13 a, serving as a solid fuel, is positioned between the cathode and theauxiliary electrode with the electrolyte contacting side of the cathodefacing the anode. Oxygen or an oxygen containing stream is fed to theoxygen interface of the cathode 11. Oxygen enters the oxygen interfaceof the cathode 11, is believed to be dissociated into atomic oxygen, andreacts with water and electrons to form hydroxyl ions at the electrolyteinterface of the cathode 11. The cathode 11 may be designed such thatoxygen enters through the edge of the cathode and flows through thecathode, or each cathode may have an oxygen contacting side and anelectrolyte contacting side, with the electrolyte contacting side beingin constant contact with an electrolyte. In the case of the cathodes 11having an oxygen contacting side and an electrolyte contacting side, theelectrochemical cell should be designed such that the oxygen contactingsides of the cathodes remain dry and constantly supplied with oxygen orair during operation. Distribution plates 14 may be placed between theelectrodes to aid in the distribution of electrolyte, hydrogen, oroxygen to the electrodes. The distribution plates 14 may also providemechanical support within the electrochemical cell unit 10 a. End plates15 are typically placed at the ends of each electrochemical cell unit 10a. The endplates 15 may be designed such that oxygen is allowed tocontact the cathode 11 through the end plate 15. The endplates 15 aredesigned to provide support to each electrochemical cell unit 10 a.

The anode and cathode of the metal-air fuel cell provide an electricalcurrent resulting from the production of electrons from the oxidation ofthe anode metal, such as zinc. When additional power is needed,electrical current may be supplied from the auxiliary electrode coupledwith the anode. The auxiliary electrode is fully charged when in itsoxidized state. Upon discharge, the auxiliary electrode undergoesreduction thereby completing the circuit and providing an electricalcurrent. The electrical current may be used to supplement the currentproduced by the fuel cell or may be used alone. To recharge theauxiliary electrode as well as the anode, a current is applied acrossthe anode and auxiliary electrode to reoxidize the auxiliary electrode.During reduction of the auxiliary electrode, metal ions contained in theelectrolyte solution are reduced and deposited back onto the anode asmetal thereby replenishing the zinc used during operation of themetal-air fuel cell. Additives may also be added to the anode or theelectrolyte to reduce the formation of dendrites and ensure a smoothuniform metallic plating when the metal is deposited on the anode.

Anodes as used in the hybrid hydrogen-oxygen alkaline fuel cellembodiment of the present invention are generally comprised of an activematerial supported on a current collector grid. The active material forthe anode of the hybrid hydrogen-oxygen alkaline fuel cell may begenerally comprised of 0.0 to 88.0 weight percent of a hydrogen storagematerial, 0.0 to 88.0 weight percent Raney Nickel, 4.0 to 12 weightpercent binder material, and 0.0 to 5.0 weight percent graphite orgraphitized carbon. The hydrogen storage material may be selected fromRare-earth metal alloys, Misch metal alloys, zirconium alloys, titaniumalloys, magnesium/nickel alloys, and mixtures or alloys thereof whichmay be AB, AB₂, or AB₅ type alloys. Such alloys may include modifierelements to increase their hydrogen storage capability.

Anodes as used in the hybrid metal-air fuel cell embodiment of thepresent invention are generally comprised of an active materialsupported on a current collector grid. The active material for the anodeas used in metal-air cells, is typically comprised of zinc, aluminum,magnesium, cadmium, or alloys or combinations thereof. Typically thesealloys will contain between 1 to 10 weight percent of indium, bismuth,lead, tin, or mercury. The active material for the anodes as used in thehybrid metal-air fuel cell in accordance with the present invention maybe generally comprised of 90 to 99 weight percent of an anode metal, and1.0 to 10 weight percent binder material. Metals such as cadmium,aluminum, or magnesium may be substituted for zinc.

The binder materials may be any material, which binds the activematerial together to prevent degradation or disintegration of theelectrode/electrode materials during the lifetime of the electrodes.Binder materials should be resistant to the electrolyte and conditionspresent within the electrochemical cell units. This includes highconcentration of KOH, dissolved oxygen, dissolved peroxyl ions (HO₂ ⁻),etc. Examples of additional binder materials, which may be added to theactive composition, include, but are not limited to, polymeric binderssuch as polyvinyl alcohol (PVA), carboxymethyl cellulose (CMC),hydroxycarboxymethyl cellulose (HCMC), and hydroxy propyl methylcellulose (HPMC). Other examples of polymeric binders includefluoropolymers. An example of a fluoropolymer is polytetrafluoroethylene(PTFE). Other examples of additional binder materials, which may beadded to the active composition, include elastomeric polymers such asstyrene-butadiene. In addition, depending upon the application,additional hydrophobic materials and/or electroconductive plastics mayalso be added to the active composition. An example of anelectroconductive polymeric binder material is based on modifiedpolyaniline and is commercially available under the trade name Panipol®(Trademark of Neste Oy Corporation).

Cathodes as used in hydrogen-oxygen alkaline fuel cells or zinc-aircells are typically comprised of a carbon matrix with a materialcatalytic toward the dissociation of molecular oxygen into atomic oxygendispersed therein. Such cathodes may be single or multilayered. A singlelayered cathode may be comprised of a carbon matrix with an activecatalytic material dispersed therein, with the carbon matrix beingsupported by at least one current collector grid. A multilayered cathodemay be composed of an active material layer having a built-inhydrophobic character, a gas diffusion layer having a greater built-inhydrophobic character than the active material layer, and at least onecurrent collector grid. The active material layer and the gas diffusionlayer are positioned adjacent to each other and supported by at leastone current collector grid. The gas diffusion layer is composed of ateflonated carbon matrix. The teflonated carbon matrix may be comprisedof 40% teflonated acetylene black carbon or 60% teflonated Vulcan XC-72carbon (Trademark of Cabot Corp.). The active material layer of thecathode in accordance with the present invention is composed of carbonparticles coated with PTFE. The carbon particles are preferably carbonblack particles, such as Black Pearl 2000 (Trademark of Cabot Corp.).The carbon/PTFE black mixture contains approximately 10 to 20 percentPTFE with the remainder being carbon black particles. An active materialcatalytic toward the dissociation of molecular oxygen into atomic oxygenis dispersed throughout the active material layer. The active catalystmaterial may be selected from silver metal, silver alloys, silver oxide,cobalt oxide, cobalt manganese oxide, cobalt, nickel, manganese oxides,manganese dioxide, pyrolyzed macrocyclics, or combinations thereof. Theactive material layer may also include up to 30 weight percent of aperoxide decomposing material. The peroxide decomposing material may beselected from MnO₂, MnO, lithium manganese oxides, lithium cobaltoxides, cobalt oxides, nickel oxides, lithium nickel oxides, ironoxides, or mixtures thereof.

The active catalyst material may be incorporated into the activematerial layer by mechanically mixing the active catalyst material withthe teflonated carbon prior to forming the electrode, or the activecatalyst material may be impregnated into the active material layerafter formation of the electrode. To impregnate the active materiallayer of the cathode with the active catalyst material after electrodeformation, the active catalyst material may be chemically orelectrochemically impregnated into the active material layer. Tochemically or catalytically impregnate the active material layer of thecathode, the cathode is dipped into an aqueous solution of an activecatalyst material precursor. The active catalyst material precursor maybe a 1M AgNO₃ solution. The reducing agent for this process will be 10%by weight sugar. Other precursors such as a AgNO₃/Ga(NO)₃ mixture,AgNO₃/LiNO₃ mixture, AgNO₃/Ni(NO₃)₂ mixture, Co(NO₃)₂, a cobalt aminecomplex, NI(NO₃)₂, Mn(NO₃)₂, cyano complexes, organo metallic complexes,amino complexes, citrate/tartrate/lactate/oxalate complexes, transitionmetal complexes, transition metal macrocyclics, and mixtures thereof maybe substituted for the AgNO₃ in the precursor solution. Once submergedin the aqueous active catalyst material precursor solution, the solutionmay be pulled into the active material layer under vacuum. The varyinglayers of hydrophobicity between the gas diffusion layer and the activematerial layer allow the solution to penetrate into the pores within theactive material layer and not penetrate into the gas diffusion layer.The active catalyst material is deposited from the aqueous solution inthe pores within the active material layer and any air or gases presentin the solution pass through the gas diffusion layer. In addition todipping in the aqueous solution, the impregnation may be performed byspraying, screen printing, or spreading the active catalyst on theelectrode surface. After removing the cathode from the active catalystmaterial solution, the cathode is dried at room temperature. The cathodeis then heat treated at 50 degrees Celsius to remove any water from theelectrode. The cathode may then be heat treated at 300–375 degreesCelsius for half an hour to decompose any remaining metal nitrates intotheir corresponding oxides. Once the oxides are formed, they will befurther decomposed to form their parent metals in a finely divided form.The particle sizes of these metals may range between 5 and 50nanometers. Temperatures exceeding this range are not employed becausethe teflon binder will begin to decompose and adversely affect theperformance of the electrodes. Depending upon the catalyst used, theseoxides may further decompose to produce their parent metal catalysts. Toadd more catalyst the above process is repeated as necessary. Thecathode is then cooled and ready for use. After impregnation, the activecatalyst material forms submicron to nano particles of the activecatalyst material within the carbon matrix. The auxiliary electrode maybe any battery positive electrode capable of withstanding the operatingconditions within the electrochemical cell. The auxiliary electrodes maybe composed of any positive electrode material supported on a currentcollector grid. The positive electrode material is generally comprisedof 75 to 85 weight percent positive electrode active material, 0.0 to 10weight percent cobalt, 0.0 to 10 weight percent cobalt oxide, and 0.0 to4.0 weight percent binder material. The cobalt and cobalt oxide areadditives which enhance conductivity or influence electrochemical steps.The positive electrode active material may be any material that mayundergo oxidation upon charging and reduction upon discharging of theelectrochemical cell. The positive electrode active material may beselected from nickel hydroxide/nickel oxyhydroxide, copper oxide, silver(I or II) oxide, manganese dioxide, or other oxides compatible with thebattery system requirements. The binder materials as used in theauxiliary electrode may be any of those listed for the anode andcathode. The auxiliary electrode is recharged by accepting an electricalcurrent from a source of power external to the hybrid fuel cell. Thesource of power may be supplied from regenerative braking, solar power,a power supply.

The electrodes in accordance with the present invention may bepaste-type electrodes or non paste-type electrodes. Non-paste typeelectrodes may be powder compacted, sinteredchemically/electrochemically impregnated, or plastic bonded extrudedtype. Paste-type electrodes may be formed by applying a paste of theactive electrode material onto a conductive substrate, compressing apowdered active electrode material onto a conductive substrate, or byforming a ribbon of the active electrode material and affixing it onto aconductive substrate. The substrate as used in accordance with thepresent invention may be any electrically conductive support structurethat can be used to hold the active composition such as a currentcollector grid selected from, but not limited to, an electricallyconductive mesh, grid, foam, expanded metal, or combinations thereof.The most preferable current collector grid for the positive electrode isnickel foam having a density of 500 g/m². For the anode, the mostpreferable current collector is an electrically conductive mesh having40 wires per inch horizontally and 20 wires per inch vertically,although other meshes may work equally well. The wires comprising themesh may have a diameter between 0.005 inches and 0.01 inches,preferably between 0.005 inches and 0.008 inches. This design providesoptimal current distribution due to the reduction of the ohmicresistance. Where more than 20 wires per inch are vertically positioned,problems may be encountered when affixing the active material to thesubstrate. The actual form of the substrate used may depend on whetherthe substrate is used for the positive or the negative electrode of theelectrochemical cell, the type of electrochemical cell (for example,battery or fuel cell), the type of active material used, and whether itis paste type or non-paste type electrode. The conductive substrate maybe formed of any electrically conductive material and is preferablyformed of a metallic material such as a pure metal or a metal alloy.Examples of materials that may be used include nickel, nickel alloy,copper, copper alloy, nickel-plated metals such as nickel-plated copperand copper-plated nickel. The actual material used for the substratedepends upon many factors including whether the substrate is being usedfor the positive or negative electrode, the type of electrochemical cell(for example battery or fuel cell), the potential of the electrode, andthe pH of the electrolyte of the electrochemical cell.

In a paste type electrode, the active electrode composition is firstmade into a paste. This may be done by first making the active electrodecomposition into a paste, and then applying the paste onto a conductivesubstrate. A paste may be formed by adding water and a “thickener” suchas carboxymethyl cellulose (CMC) or hydroxypropylmethyl cellulose (HPMC)and a binder, such as teflon, to the active composition. The paste wouldthen be applied to the substrate. After the paste is applied to thesubstrate to form the electrode, the electrode may be sintered. Theelectrode may optionally be compressed prior to sintering. The teflonbinder is added to the composition so that upon sintering the electroderetains ites integrity even when operating in a flooded electrolytemode.

To form the electrodes by compressing the powdered active electrodematerial onto the substrate, the active electrode material is firstground together to form a powder. The powdered active electrode materialis then pressed or compacted onto a conductive substrate. Aftercompressing the powdered active electrode material onto the substrate,the electrode may be sintered. To form the electrodes using ribbons ofthe active electrode material, the active electrode material is first isground into a powder and placed into a roll mill. The roll millpreferably produces a ribbon of the active electrode material having athickness ranging from 0.018 to 0.02 inches, however, ribbons with otherthicknesses may be produced in accordance with the present invention.Once the ribbon of the active electrode material has been produced, theribbon is placed onto a conductive substrate and rerolled in the rollmill to form the electrode. After being rerolled, the electrode may besintered.

The electrode may be sintered in the range of 170 to 180° C. so as notto decompose the conductive polymer, as compared to sinteringtemperatures in the range of 310 to 330° C. if the conductive polymer isnot utilized in the electrode.

EXAMPLE 1

A hybrid hydrogen-oxygen alkaline fuel cell in accordance with thepresent invention was constructed and tested. The hybrid hydrogen-oxygenalkaline fuel cell included a cathode, two anodes, and an auxiliaryelectrode. One of the anodes was constructed to operate with the cathodeas a fuel cell and the other anode was constructed to operate with theauxiliary electrode as a battery.

The cathode for the hybrid hydrogen-oxygen alkaline fuel cell wasprepared by first depositing the gas diffusion layer composed of 45weight percent teflonated carbon (acetylene black Shawinigan AB) onto acurrent collector grid. Approximately 6–10 g of gas diffusion layermaterial was deposited onto the current collector grid per 100 cm². Theactive material layer composed of 20 weight percent teflonated carbon(Black Pearl 2000, trademark of Cabot Corp.) was then deposited onto thegas diffusion layer. Approximately 2–3 grams of active material layermaterial is deposited onto the gas diffusion layer per 100 cm². Afterdepositing the gas diffusion layer, a second current collector grid isplaced on top of the active material layer to complete the cathode. Thecathode was hot pressed at 320° C. at a pressure of 0.3 tons per cm² fortwo minutes after the temperature was reached. The cathode wassubsequently cooled to room temperature.

The active material layer of the cathode was then impregnated with anactive catalyst material. The cathode was dipped into an aqueoussolution of an active catalyst material precursor. The active catalystmaterial precursor was a 1M AgNO₃ solution preceded by a 10 percent byweight sugar solution dip as a reducing agent. Once submerged in theaqueous active catalyst material precursor solution, the solution waspulled into the active material layer under vacuum. The varying layersof hydrophobicity between the gas diffusion layer and the activematerial layer allowed the solution to penetrate into the pores withinthe active material layer and not penetrate into the gas diffusionlayer. After removing the cathode from the active catalyst materialsolution, the cathode was dried at room temperature. The cathode wasthen heat treated at 50 degrees Celsius to remove any water from theelectrode. The cathode was then heat treated at 300–375 degrees Celsiusfor half an hour to decompose any remaining nitrates into oxides andthen into their parent metals. The cathode was then cooled andincorporated into the hybrid hydrogen-oxygen alkaline fuel cell.

The anode designed to operate with the cathode as a fuel cell included agas diffusion layer and an active material layer. The gas diffusionlayer was composed of 60% teflonated carbon (Vulcan XC-72) rolled into aribbon. The active material layer was prepared by forming a mixturecomposed of 88 weight percent Raney nickel, 8.0 weight percent teflon,and 4.0 weight percent graphite (Timcal KS 75). The mixture was thenrolled into ribbons of active anode material. The active material layerribbon and the gas diffusion layer ribbon were placed between twocurrent collector grids and re-rolled to form the hydrogen electrode.The anode was sintered in nitrogen at 350° C. for half an hour thencooled to room temperature in a nitrogen environment.

The anode designed to operate with the auxiliary electrode also includeda gas diffusion layer and an active material layer. The gas diffusionlayer was prepared in the same manner as the gas diffusion layer for theanode designed to operate with the cathode. The active material layer,however, was formed from a mixture composed of 88 weight percent Mischmetal, 8.0 weight percent teflon, and 4.0 weight percent graphite. Themixture was then rolled into ribbons of active anode material. Theactive material layer ribbon and the gas diffusion layer ribbon wereplaced between two current collector grids and re-rolled to form thehydrogen electrode. The anode was sintered in nitrogen at 350° C. forhalf an hour then cooled to room temperature in a nitrogen environment.

The auxiliary electrode was prepared by first forming a standard pastecomposed of 88.6 weight percent nickel hydroxide material withco-precipitated zinc, cobalt, calcium, and magnesium (91.4 atomicpercent nickel hydroxide, 2.4 atomic percent cobalt, 5.6 atomic percentzinc, 0.5 atomic percent calcium, and 0.1 atomic percent magnesium), 5.0weight percent cobalt, 6.0 weight percent cobalt oxide, and 0.4 weightpercent polyvinyl alcohol binder. The paste was then affixed to acurrent collector grid to form the auxiliary electrode.

The hybrid hydrogen-oxygen alkaline fuel cell was tested underdischarging conditions and tested for recharging capability. The resultsfor the hybrid hydrogen-oxygen alkaline fuel air cell are shown in FIG.12, FIG. 13, and below in Table 1. FIG. 12 shows the current (dashedline) and the voltage of the fuel cell only and the voltage of the fuelcell and battery together. The voltages were measured during a 3 Adischarge and a 20 second pulse discharge of 9.6 A. The hybridhydrogen-oxygen alkaline fuel cell achieved an increased voltage whenboth the cathode and the auxiliary electrode battery operated in tandemwith the respective anodes as compared to the cathode operating alonewith the respective anode. FIG. 13 shows voltage (□) of the hybrid fuelcell when a pulse current (⋄) is applied to the cell. The voltage of thehybrid cell steadily increased upon receiving a series of 30 second 1ampere pulse charges.

TABLE 1 At 10 sec. 3 A pulse At 10 sec. 9.6 A discharging pulsedischarging Cathode Only Cell voltage: 0.7095 V Cell Voltage: 0.2759 VCathode and Cell Voltage: 1.1080 V Cell Voltage: 0.8782 V Auxiliaryelectrode ΔV 0.3985 V 0.5723 V Voltage % increase 55.8% 207%

EXAMPLE 2

A hybrid metal air fuel cell in accordance with the present inventionwas constructed and tested. The hybrid metal-air fuel cell included acathode, an anode, and an auxiliary electrode. The anode was designed tooperate with the cathode as a fuel cell and operate with the auxiliaryelectrode as an battery.

The cathode for the hybrid metal-air fuel cell was prepared by firstdepositing the gas diffusion layer composed of 60 weight percentteflonated carbon (Vulcan XC-72) onto a current collector grid.Approximately 6–10 g of gas diffusion layer material was deposited ontothe current collector grid per 100 cm². The active material layercomposed of 20 weight percent teflonated carbon was then deposited ontothe gas diffusion layer. Approximately 2–3 grams of active materiallayer material is deposited onto the gas diffusion layer per 100 cm².After depositing the gas diffusion layer, a second current collectorgrid is placed on top of the active material layer to complete thecathode. The cathode was then hot pressed at a pressure of 0.3 tons percm² at a temperature of 320° C. for 2 minutes and subsequently cooled toroom temperature. The active material layer of the cathode was thenimpregnated with an active catalyst material. The cathode was dippedinto an aqueous solution of an active catalyst material precursor. Theactive catalyst material precursor was a 1M AgNO₃ solution containing10% by weight sugar as a reducing agent. Once submerged in the aqueousactive catalyst material precursor solution, the solution was pulledinto the active material layer under vacuum. The varying layers ofhydrophobicity between the gas diffusion layer and the active materiallayer allowed the solution to penetrate into the pores within the activematerial layer and not penetrate into the gas diffusion layer. Afterremoving the cathode from the active catalyst material solution, thecathode was dried at room temperature. The cathode was then heat treatedat 50 degrees Celsius to remove any water from the electrode. Thecathode was then heat treated at 300–375 degrees Celsius for half anhour to decompose any remaining nitrates into oxides. The cathode wasthen cooled and incorporated into the hybrid metal-air fuel cell.

The anode for the hybrid metal-air fuel cell was prepared by forming amixture composed of 98.7 weight percent zinc powder, 1.0 weight percentteflon, and 0.3 weight percent carboxymethyl cellulose and then mixed toform a paste. The paste was then applied onto nickel foam, dried and afinal roll compaction to the desired electrode thickness of 0.02 inches.

The auxiliary electrode was prepared by first forming a standard pastecomposed of 88.6 weight percent nickel hydroxide material withco-precipitated zinc, cobalt, calcium, and magnesium (91.4 atomicpercent nickel hydroxide, 2.4 atomic percent cobalt, 5.6 atomic percentzinc, 0.5 atomic percent calcium, and 0.1 atomic percent magnesium), 5.0weight percent cobalt, 6.0 weight percent cobalt oxide, and 0.4 weightpercent polyvinyl alcohol binder. The paste was then affixed to acurrent collector grid to form the auxiliary electrode.

The hybrid metal air cell was first tested for discharge conditions. Theresults for the hybrid metal air fuel cell are shown in FIG. 14 andbelow in Table 2. FIG. 14 shows the current (dashed line) and thevoltage of the fuel cell only and the voltage of the fuel cell andbattery together. The voltages were measured during a 3 A discharge anda 20 second pulse discharge of 9.6 A. The hybrid metal air cell achievedan increased voltage when both the cathode and the auxiliary electrodebattery operated in tandem with the anode as compared to the cathodeoperating alone with the anode.

TABLE 2 At 10 sec. 3 A pulse At 10 sec. 9.6 A discharging pulsedischarging Cathode Only Cell voltage: 1.1096 V Cell Voltage: 0.7531 VCathode and Cell Voltage: 1.5725 V Cell Voltage: 1.3507 V Auxiliaryelectrode ΔV O.4629 V 0.5976 V Voltage % increase 41.7% 79.4%

The foregoing is provided for purposes of explaining and disclosingpreferred embodiments of the present invention. Modifications andadaptations to the described embodiments, particularly involving changesto the shape of the fuel cell and components thereof, the physicalarrangement of the battery electrodes and the fuel cell electrodes, andvarying electrode compositions will be apparent to those skilled in theart. These changes and others may be made without departing from thescope or spirit of the invention in the following claims.

1. A vehicle drive system comprising: an electric motor; a hybrid fuelcell comprising a fuel cell portion and a rechargeable battery portion;and a hydrogen storage unit for storing and supplying hydrogen to saidhybrid fuel cell; said fuel cell portion and said rechargeable batteryportion operating alone or in tandem to power said electric motor; saidfuel cell portion and said rechargeable battery portion sharing at leastone reactant.
 2. The vehicle drive system according to claim 1, whereinsaid hybrid fuel cell further comprises an anode section including oneor more anodes shared between said fuel cell portion and saidrechargeable battery portion.
 3. The vehicle drive system according toclaim 2 wherein said anode comprises an anode active material, saidanode active material including zinc, cadmium, magnesium, or aluminum.4. The vehicle drive system according to claim 3, wherein said anodecomprises 90 to 99 weight percent of said anode active material and 1 to10 weight percent of a binder material.
 5. The vehicle drive systemaccording to claim 2, wherein said anode comprises a hydrogen storagematerial and/or Raney nickel.
 6. The vehicle drive system according toclaim 5, wherein said anode comprises 0.0 to 88.0 weight percent of saidhydrogen storage material, 0.0 to 88.0 weight percent Raney. nickel, 4.0to 12.0 weight percent of a binder material, and 0.0 to 5.0 weightpercent of a conductive material.
 7. The vehicle drive system accordingto claim 6, wherein said conductive material comprises graphite orgraphitized carbon.
 8. The vehicle drive system according to claim 6,wherein said hydrogen storage material comprises Rare-earth metalalloys, Misch metal alloys, zirconium alloys, titanium alloys,magnesium/nickel alloys, or mixtures thereof.
 9. The vehicle drivesystem according to claim 2, wherein said fuel cell portion comprises atleast one cathode, said cathode being in electrical communication withsaid anode.
 10. The vehicle drive system according to claim 9, whereinsaid cathode comprises a carbon matrix with an active catalyst materialcatalytic toward the dissociation of molecular oxygen dispersed therein.11. The vehicle drive system according to claim 10, wherein said activecatalyst material is selected from silver, silver alloys, silver oxide,cobalt, cobalt oxide, cobalt manganese oxide, nickel, manganese oxide,manganese dioxide, pyrolyzed macrocyclics, or combinations thereof. 12.The vehicle drive system according to claim 10, wherein said cathodefurther comprises a peroxide decomposing material.
 13. The vehicle drivesystem according to claim 2, wherein said rechargeable battery portioncomprises at least one auxiliary electrode, said auxiliary electrodebeing in electrical communication with said anode.
 14. The vehicle drivesystem according to claim 13, wherein said auxiliary electrode comprisesa positive electrode material.
 15. The vehicle drive system according toclaim 14, wherein said auxiliary electrode is a nickel electrode. 16.The vehicle drive system according to claim 14, wherein said auxiliaryelectrode is a silver electrode.
 17. The vehicle drive system accordingto claim 14, wherein said positive electrode material comprises 75 to 85weight percent of a positive electrode active material, 0.0 to 10 weightpercent cobalt, 0.0 to 10 weight percent cobalt oxide, and 0.0 to 4.0weight percent of a binder material.
 18. The vehicle drive system cellaccording to claim 17, wherein said positive electrode active materialis selected from nickel hydroxide/nickel oxyhydroxide, copper oxide,silver oxide, manganese dioxide, or combinations thereof.
 19. Thevehicle drive system according to claim 1, wherein said rechargeablebattery portion is adapted to accept an electrical current from a sourceof power external to said hybrid fuel cell.
 20. The vehicle drive systemaccording to claim 1, wherein said rechargeable battery portion isadapted to accept an electrical current produced by said fuel cellportion.
 21. The vehicle drive system according to claim 1, wherein saidfuel cell portion and said rechargeable battery portion share anelectrolyte.
 22. The vehicle drive system according to claim 1, whereinsaid hydrogen storage unit comprises a pressure containment vessel atleast partially filled with a hydrogen storage alloy.
 23. The vehicledrive system according to claim 1, wherein said hydrogen storage unitcomprises a pressure containment vessel adapted to store hydrogen inliquid or gaseous form.